code: def test_get_item_returns_base_value_when_no_override(self):
      self.override_dict.set_base("a", 42)
      self.override_dict.set_base("b", 0)
  
      self.assertEqual(self.override_dict["a"], 42)
      self.assertEqual(self.override_dict["b"], 0)
      self.assertEqual(len(self.override_dict), 2)
  
imports: from typing import Sequence
  from torch.onnx import errors
  from torch.onnx._internal import registration
  from torch.testing._internal import common_utils
label_desc: Use image node_id 2 for calling the TestOverrideDict obj's underlying member method code with example usage: obj.test_get_item_returns_base_value_when_no_override() without return types